1. Field of the Invention
The present invention relates to an antenna for small size electronic equipment.
2. Description of Related Art
As earlier developed electronic equipment that utilizes electric wave information by receiving the electric wave, there is an electronic wristwatch that performs time adjustment automatically by receiving electronic wave of the standard time.
As an antenna provided in such an electronic wristwatch to receive the electric wave, it has been known to form an antenna by winding a coil on a core material which comprises a magnetic material with a good reception sensitivity such as ferrite, amorphous or the like as disclosed in Japanese Patent Laid-Open Publication No. 2001-337181.
It has also been known that the reception sensitivity of an antenna is affected by the shape of the core material and is improved when both ends of the core material are enlarged. For example, the both ends of the core material can be easily enlarged by a molding that has certain degree of freedom in designing the shape, so that the reception sensitivity can be improved.
However, for example, when the core material is formed by laminating a plurality of thin plates made of the magnetic material or binding a plurality of wire rods made of the magnetic material, the degree of freedom in designing the shape is limited. Thus, a thickness of the core material is constant and the optimization of the shape of the core material to the reception sensitivity has not been accomplished.